TOOTH DECAY AND FILLINGS
Tooth decay is damage caused by acid producing bacteria on the surface of the teeth which form a biofilm known as plaque. If this damaged, softened tooth collapses into a hole, this is known as a cavity.
Eating sugar is a key cause of dental decay. When you eat fermentable carbohydrates (sugars), the bacteria on your teeth break these down and produce acid, which is what causes the damage. The acid makes the tooth become softer and more sponge-like for up to 40 minutes after you stop eating. After this time your saliva helps to neutralise the acid and the tooth re-strengthens. However, if you then eat more sugar, the process happens again, meaning that for a large proportion of the day, the teeth are soft and starting to break down. This is why it is important to keep food intake to a minimum (in terms of frequency of eating) and we recommend that you shouldn’t eat more than 5 times per day and should brush 2 times. If you want to have something sugary, it is best to eat it with a meal and over a shorter time frame.
If decay is very superficial, sometimes (not always) a high fluoride toothpaste, excellent oral hygiene and added fluoride varnish applied to the tooth by your dentist can help re-strengthen the tooth and prevent progression which may even mean that you do not need a restoration (filling). However, if the decay has progressed through the enamel (outermost surface) of the tooth, it is likely the decayed tooth tissue needs to be removed and a filling material placed to replace it. Filling materials can be metal (amalgam), white (composite) and occasionally glass ionomer which is also white. Usually, a local anaesthetic is required to numb the site and ensure your treatment is painless. Depending on the size of the cavity, most simple fillings take less than 30 minutes to complete and the numbness wears off around 1-4 hours later, depending which technique was used.
Sometimes, having decay is painless, however as the size of the lesion progresses, you may start to get short, sharp pains on drinking something cold, that don’t usually last very long. This is due to inflammation in the nerve of the tooth as a result of toxins produced by the bacteria in the decayed site. If the inflammation is long standing, the nerve may start to die leading to spontaneous pain which can be worsened by heat, and it often wakes patients up at night. This is known as irreversible pulpitis, because the pulp is irreversibly inflamed. Occasionally, a tooth can be restored and still progress to irreversible pulpitis. The treatment options for a tooth with irreversible pulpitis are often restricted to either root canal treatment or extraction.
Once the nerve of the tooth dies, the pulp starts to break down causing products that discolour the tooth. This can explain why some dead teeth change colour and are noticeably darker (see the tooth whitening page for more information on what can be done about this). When the pulp is broken down, bacteria can move in to this space and eventually reach the tip of the tooth, known as the apex. The bacteria can cause an inflammation at the apex, resulting in pain on biting but no sensitivity to cold or heat. This is known as apical periodontitis. An abscess may form, where the space at the apex becomes filled with pus (bacteria and white bloods cells trying to fight the infection) which can be extremely painful and severely tender to bite on. Once the nerve of the tooth is dead, the treatment options are to remove the dead tissue and replace it with a dental material (root canal treatment) or remove the tooth. If you want to know more about root canal treatments, have a look at the procedures section of my website. Antibiotics are only indicated if the infection has caused you to be unwell, if the infection is too large to get numb (pus is very acidic which can occasionally reduce the effectiveness of anaesthetics used) or if there is another reason why treatment is not possible at the time. Antibiotics do not treat dental decay and will not prevent the abscess reforming.
Interestingly, some patients have a mixture of these symptoms, so further tests might be required (such as radiographs, testing to see if the tooth is alive and testing if the tooth is tender to touch) to establish a definitive diagnosis. That’s why it is important you seek professional advice for tooth ache and the sooner it is managed, the better to prevent progression of the disease.